Liquid metal heated steam generator



May 17, 1966 w, n c so 3,251,404

LIQUID METAL HEATED STEAM GENERATOR Filed Dec. 26, 1961 INVENTOR. ROBERT W. DICKINSON ATTORNEY United States Patent 3,251,404 LIQUID METALHEATED STEAM GENERATOR- .Robert W. Dickinson, Northridge, Califi, assignor to North American Aviation, Inc. Filed Dec. 26, 1961, Ser. No. 161,871 10 Claims. (Cl. 165-32) ,The present invention is directed to vapor generators and more particularly to liquid metal heated steam generators.

In the prior art liquid metal heated steam generators severe structural limitations are imposed by the contact of the liquid metal with the junction between the boiler tubes and associated headers because of the high thermal stresses present at these junctions. Thus, thick tube sheets are conventionally used in order to accommodate the high thermal stresses resulting in significantly increased cost and difficulty in fabrication and assembly. (See Nucleonic's, vol. 19, No. 1, January 1961, pp. 65-70.)

It is therefore the primary object of the present invention to provide a simple, less costly vapor generator. I

Another object of the present invention is to provide a vapor generator in which all pressure-containing components are circular in cross section, thereby reducing metal thickness and fabrication costs.

Another object of the present invention is to provide a steam generator capable of unlimited steam generating capacity by increasing the number of tubes and length of the unit.

Another object of the present invention is to provide a liquid metal heated steam generator in which the junction of the boiler tubes and headers is protected from contact with the liquid metal.

A further object of the present invention is to provide a liquid metal heated steam generator which is simple and relatively free from thermal stresses induced by rapidly changing liquid metal temperatures.

These and other objects of the present invention will be more apparent from the following detailed description and the drawing, made a part hereof, in which:

FIG. 1 is a perspective view of the preferred embodiment of the present invention;

FIG. 2 is a partially sectioned end view of the lower shell member of FIG. 1;

FIG. 3 is a partially sectioned side 'view of the upper shell member of FIG. 1;

FIG.- 4 shows the gas pressure control system of the present invention; and

FIG. 5 is a sectioned end view of a second embodiment of the present invention.

Referring now to the drawing in detail, FIG. 1 shows the preferred arrangement of the steam generator of the present invention which comprises an upper shell member 20 having a primary coolant inlet 22 and a secondary coolant outlet 24. One or more tube shells 26 are connected to the bottom of shell member 20 and to the bottom of a lower shell member 28. The lower shell member has a primary coolant outlet 30 and a secondary coolant inlet 32. Each of the shell members 20 and 28 have an inert gas inlet pipe 34 located in their top surface and communicating with the interior volume of the respective member. The upper and lower shell members are essentially identical in every structural detail.

Both the primary coolant inlet 22 and outlet 30 of the shell members 20 and 28, respectively, communicate directly with the interior volume of these shell members and the tube shells 26. In this manner the primary coolant entering through inlet 22 passes through shell member 20 down through tube shells 26 into shell member 28 and out through outlet 30.

The secondary coolant inlet 32 passes through the wall ice of shell 28 and is connected to and communicates with the interiorvolume of an inlet header 36 (see'FIG. 2)

20 above the primary coolant level 37. Thus the primary.

coolant entering shell member 20 through inlet 22 passes out of shell 20 through tube shells 26 without contacting the outlet header 40. The inlets and outlets of the primary and secondary coolants, as well as the shells and headers, are located in parallel relationship to each other with the shell tubes 26 and secondary coolant tubes 38 located normal to the axes of those elements.

The volume above the primary coolant level 37 in both the upper and lower shell members 20 and 28 contains a pressurized gas 39, inert to the primary coolant. The gas is maintained at a predetermined but controllable pressure through inlet pipes 34. The pipes 34 are connected to a pressure control valve 42 (see FIG. 4) which controls the gas pressure from gas source- 44 in accordance with a predetermined setting. The valve 42 may v and gas source.

be made responsive to the primary coolant level 37 in both the upper and lower shell members 20 and 28 through the use of, a standard level sensing gauge. Further, each shell 20 and 28 may have an independent valve primary coolant liquid level below the inlet and outlet headers 36 and 40 and also functions as a surge volume for the coolant;

In the preferred system where a liquid metal, e.g. so-,

dium, is used for the primary coolant and water is used for the secondary coolant the gas blankets protect the junction of boiler tubes 38 and headers 36 and 40 for feedwater and high pressure steam from the liquid metal. This blanket permits the use of the steam generator as a surge tank, thereby eliminating the requirement for a separate liquid metal expansion tank and essentially eliminates thermal stress problems induced by rapidly changing liquid metal temperatures. It is within the purview of the invention to use stilling bafiies or splash bafiies in the upper and lower shells 20 and 28.

In the preferred embodiment both the shell members 20 and 28 and the headers 36 and 40 are of circular cross section for ease in fabrication and maximum strength. While the preferred embodiment describes the headers 36 and 40 as contained within the shell 28 and 20, respectively, it is within the contemplation of the present invention to locate the headers in a position where only the lower surface thereof is within the shell. This embodiment of the invention is shown in FIG. 5 within the shell 50 has an inlet or outlet 51, a tube shell 52 connected to its bottom surface, and a secondary coolant header 53 positioned along its top surface with a portion of the header 53 exposed for easy access for repair. The liquid ment of the invention is shown in FIG. 5 wherein the shell shell 50 thereby allowing greater exposure of surface area of the secondary coolant tubes 38 to the primary coolant.

In this embodiment both the shell 50 and header 53 are The inert gas pressure maintains the 3 apparent to those skilled in the art without departing from the scope of the invention. Therefore, the present invention is not limited to the specific embodiment disclosed but only by the appended claims.

What is claimed is:

1. Heat exchanging apparatus comprising first and second shell members, at least one shell tube extending between and structurally connected directly to said members, first and second headers, each of said first and second headers having at least a portion of its surface sealed within one of said first and second shell members respectively, a plurality of U-shaped tubes interconnecting said header portions and passing through said shell tube, said shell members and shell tube being adapted to pass a first coolant, said headers and tubes being adapted to pass a second coolant, and means including a pressurized gas for maintaining the liquid level of said first coolant out of contact.

with said first and second headers.

2. The heat exchanging apparatus for claim 1 wherein said first and second headers are located and supported within said first and second shell members respectively, and said means includes pressure control means.

3. The heat exchanging apparatus of claim 1 wherein said shell members and said headers have a circular cross section and have parallel longitudinal axes.

4. The heat exchanging apparatus of claim 1 wherein said first coolant is a liquid metal and said pressurized gas is inert with respect to said metal.

5. The heat exchanging apparatus of claim 1 wherein said at least one shell tube connects the bottom of said first shell member with the bottom of said second shell member.

6. The heat exchanging apparatus of claim 1 having a first coolant inlet connected to said first shell member, a first coolant outlet connected to said second shell member, a second coolant inlet connected to said second header, and a second coolant outlet connected to said first header.

7. The heat exchanging apparatus of claim 1 having a plurality of shell tubes, each of said shell tubes having a bundle of said plurality of tubes passing through it in parallel spaced relation between said first and second headers.

8. The heat exchanging apparatus of claim 1 wherein said last-named means includes a pressurized gas inlet in 4 the top surface of each of said first and second shell members.

9. The heat exchanging apparatus of claim 1 wherein said first coolant is sodium and said second coolant is water and said sodium level in each of said first and second shell members is maintained below the bottom surface of said headers and out of contact with the junction of said plurality of tubes with each of said headers.

10. A liquid metal heated steam generator comprising a first shell member, a liquid metal inlet connected to said first shell member, a second shell member, a liquid metal outlet connected to said second shell member, at least one shell tube connecting the lower portion of said first shell to the lower portion of said second shell, an outlet steam header having at least its lower portion sealed within said first shell member, an inlet water header having at least its lower portion sealed within said second shell member, a plurality of U-shaped steam generating tubes connecting the lower portion of said inlet water header to the lower portion of saidoutlet steam header, said steam generating tubes passing through said shell tubes in parallel spaced relation, a steam outlet connected to said outlet header, a water inlet connected to said inlet header,

and means including an inert gas surrounding at least the References Cited by the Examiner UNITED STATES PATENTS 1,531,777 3/1925 Frost -143 2,229,554 l/ 1941 Cummings 122-32 3,000,364 9/1961 Steever 165-134 3,059,908

l0 /1962 Fox et al. 165-134 ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner. 

10. A LIQUID METAL HEATED STEAM GENERATOR COMPRISING A FIRST SHELL MEMBER, A LIQUID METAL INLET CONNECTED TO SAID FIRST SHELL MEMBER, A SECOND SHELL MEMBER, A LIQUID METAL OUTLET CONNECTED TO SAID SECOND SHELL MEMBER, AT LEAST ONE SHELL TUBE CONNECTING THE LOWER PORTION OF SAID FIRST SHELL TO THE LOWER PORTION OF SAID SECOND SHELL, AN OUTLET STEAM HEADER HAVING AT LEAST ITS LOWER PORTION SEALED WITHIN SAID FIRST SHELL MEMBER, AN INLET WATER HEADER HAVING AT LEAST ITS LOWER PORTION SEALED WITHIN SAID SECOND SHELL MEMBER, A PLURALITY OF U-SHAPED STEAM GENERATING TUBES CONNECTING THE LOWER PORTION OF SAID INLET WATER HEADER TO THE LOWER PORTION OF SAID OUTLET STEAM HEADER, SAID STEAM GENERATING TUBES PASSING THROUGH SAID SHELL TUBES IN PARALLEL SPACED RELATION, A STEAM OUTLET CONNECTED TO SAID 